title: The effects of high levels of rumen degradable protein on rumen pH and histamine concentrations in dairy cows.
abstract: An experiment was conducted to test the hypothesis that the supplementation of crude protein (CP) results in rumen acidosis and increased histamine concentrations in dairy cows. Six ruminally fistulated, non-pregnant dry cows were fed three experimental rations in a replicated 3 × 3 Latin square design. The CP contents in the low-CP, the high rumen undegradable protein (high-RUP) and the high rumen degradable protein (high-RDP) rations were 112, 259 and 266 g/kg dry matter (DM) respectively. The cows were fed 7.7 kg DM of the concentrates and 2.7 kg DM of rice straw. High levels of RDP in the ration significantly increased the ammonia, total volatile fatty acid (VFA) and histamine concentrations in the rumen fluid. However, supplemental CP, whether degradable or undegradable, did not significantly affect the pH of rumen fluid. Plasma urea nitrogen concentration was higher in both high-RDP and high-RUP in relation to cows fed the low-CP ration. The rise in ruminal histamine concentrations was physiologically non-relevant, most likely because rumen pH was not affected by supplemental CP at the installed level of DM intake. Therefore, it can be concluded that the issue of supplemental CP, rumen pH and ruminal histamine concentrations has not yet been settled. Further research is warranted to understand these relationships.
authors.affiliation: Animal Nutrition Division, Department of Farm Animal Health, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands.
authors.forename: R
authors.initials: R
authors.lastname: Pilachai
authors.forename: J Th
authors.initials: JT
authors.lastname: Schonewille
authors.forename: C
authors.initials: C
authors.lastname: Thamrongyoswittayakul
authors.forename: S
authors.initials: S
authors.lastname: Aiumlamai
authors.forename: C
authors.initials: C
authors.lastname: Wachirapakorn
authors.forename: H
authors.initials: H
authors.lastname: Everts
authors.forename: W H
authors.initials: WH
authors.lastname: Hendriks
mesh_terms: D000821:Animal Feed / Q000032:analysis; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D001806:Blood Urea Nitrogen; D001826:Body Fluids / Q000737:chemistry / Q000378:metabolism*; D002417:Cattle; D003612:Dairying; D004032:Diet / Q000662:veterinary; D004044:Dietary Proteins / Q000494:pharmacology*; D005232:Fatty Acids, Volatile / Q000737:chemistry; D005260:Female; D006632:Histamine / Q000032:analysis*; D006863:Hydrogen-Ion Concentration; D012417:Rumen / Q000737:chemistry* / Q000187:drug effects; D013025:Glycine max / Q000737:chemistry
chemical_list: D004044:Dietary Proteins; D005232:Fatty Acids, Volatile; D006632:Histamine